Cattle are fed rations that include fodder, silage, and protein supplements. The fodder includes grasses and other plants such as clover and alfalfa. Silage is various green plants that are chopped into small pieces and fermented in a silo. The protein supplement is usually ground or palletized grain. Grains that are commonly used include corn, milo, soy beans, barley and oats. Alfalfa can be processed and used as a protein supplement. Fish meal has also been used as a protein supplement in the past.
The fodder is dried and baled in most cases. The bales are generally large round bales or large rectangular bales. Both large round and rectangular bales generally weigh between 1,200 and 2,000 pounds. Such bales can be handled and transported economically. Fodder can also be dried and stored in loose stacks.
The fodder is mixed with silage and or with a protein supplement. The fodder is reduced to relatively small pieces either before or during mixing with either silage or a protein supplement. Cows will leave large pieces of coarse fodder and eat only the silage and protein supplement if the fodder is not reduced to a small particle size. Machines for reducing fodder include hammer mill grinders and vertical spindle mixers.
The vertical spindle mixers have a large tub with an open top. One or more vertical spindles are mounted on the floor of the tub. These spindles include auger flighting and bars with sharp or toothed edges attached to the auger flighting. Rotating the spindle or spindles reduces the fodder in a large bale to small pieces within a few minutes. Silage and a protein supplement can be mixed with fodder in the mixer. After the feed in the tub is reduced and mixed, a discharge door in a side wall of the tub is opened and the feed is forced through the door by an auger. A single spindle mixer discharges the feed through the discharge door and cleans the tub floor rapidly. Large mixers with two or three vertical spindles also discharge the material rapidly but tend to leave some fodder on the tub floor. Some of the feed tends to be passed from one spindle to another spindle rather than being discharged through the discharge opening after the tub is mostly emptied.